Method of and apparatus for making molded articles



J. GREGG May 31, 1949.

METHOD OF AND APPARATUS FOR MAKING MOLDED ARTICLES 3 Sheets-Sheet 1 Filed Aug. ll, 1945 C] //ENTOR BY l? gz AII'TORNEY May 31, 1949. J'. GRI-:GG 2,471,739

METHOD OF AND APPARATUS FOR MAKING MOLDED ARTICLES Filed Aug. ll, 1945 3 Sheds-Sheet 2 TTORNEY May 31, 1949. J. GRI-:GG 2,471,739

METHOD OF AND APPARATUS FOR MAKING MOLDED ARTGLES Filed Aug. ll, 1945 3 Sheets-Shea?l 5 INVENTOR Jazz Gregg ATTORNEY Patented May 31, 1949 UNITED STATES METHOD. OF AND APPARATUS FOR'MAKLING.-

MOLDED ARTICLES This inventionY relates `to methods of and apparatus for making molded articles. It is particularly directed to molding by use of high irequency current passed through the article to be molded.

An object of this invention is to provide a method of the character described comprising preheating a mold, then subjecting the article to bel moldedV in the mold to high vfrequency current, and thereafter post-heating the mold.

The mold has top and bottom conductor plates at the top and bottom of the mold cavity. The preheating of the mold. is for the purpose of having the top and :bottom plates at a temperature equal to or slightly higher than the temperature to which the article to be molded is heated in the high frequency'apparatus, because unless the top and bottom plates are atsuch temperature, the high frequency apparatus will cause all of said article to reach curing or molding temperature at exactly the same time, and should the conductor surfaces contacting said article not be at said temperature, these surfaces will extract heat from the surfaces ofthe article, contiguous thereto, and reduce the temperature of such surfaces below the proper curing or molding temperature, or at least belowr the temperature existent in the interior of the molded article, thereby retarding, if not arrestingthe curing or molding process adjacent such surfaces. In accordance with the present invention, the top and bottom plates, above and below the cavity, constitute terminals forming part of the circuit in the high `frequency apparatus-embodying the invention. These terminals are preheated.

The purpose of the high frequency current is to heat the article to be molded 4to curing temperature or to plasticizing or fusing temperature, which permits start of the vcuring quickly since the high frequency current brings the temperature of the article to be molded, `to curing temperature quickly. The high frequency current is applied to each mold only for sufficient time `to bring the article to be cured ormolded to curing temperature.

The purpose lof) the post-heating is to keep the two metal terminals or plates above and below the mold cavity, at curing temperature or` slightly higher so as Vto retain the article molded atcuring temperature. The mold in accordance with the present invention is post-heated until the rubber or `other plastic material is:plasticized, molded or cured.

Another objectof'this .invention is'to provide a highly improved apparatus loftheV character` de- 2% scribed including-'.means` for preheating a mold while the moldljis' carried.; on a.conveyor, and means for conveyingthemold.through a high frequency apparatus where-the article to bemolded is subjected to high'frequency current, and means to convey.. th'e mold l,through .a post-heater.

Another object' offthis vinvention is to provide high frequencyapparatus yof the character described', incll'ldi'ngfa conveyor, and a mold vcarried by the conveyor andiprovidedwith top and bottom plates at'thetop and'A bottom `of the mold cavity and constituting.A terminals in contact with bus bars conrlectedto` a high frequency generator.

Another object of thisinvention is to provide a high frequency apparatusof the character described,includingyaI sectional cover member which may be uncovered in: sections to expose the molds carried by the conveyor.'

Yetanother object of r'this invention is yto provide an improvedapparatusof vthe character described, including'a preheater, a conveyor to carry the molds through the preheater to a high frequency apparatus,: a high.` frequency apparatus, includn'ga conveyorto receive the molds from theV preheater,l and" carrying the molds through the high* frequency apparatus, and a post-heater" inclulzli'ng' a.: conveyor to take the molds from' the high frequency apparatus and move the. latter throughth'e post-heater.

Still .another object .ofv this vinvention isto provide a strong andfz-durableapparatus of the character. described whiclrshalfbe,economical to operate, which shall be 'smooth and `positive in operation, and yet practical "andfefcientto a high degree'inuse.v

Still anotherfobject ofthis invention is to provide a highly A'improved'process ofthe character describedwhichshall be simpleY andx'easy to carry out, whiclrshall'make goodrnoldedobjects with a niinimum'oflabor,v andzsavingi in time and costs;

Other objectspffiths .invention will in'part be obvious and A-in part':hereinafterpointed out.

The' inventionaccordngly;.consists in the `combin-ation `of steps; features ofconstruction, combinations of elements;and-'arrangement of parts which-'will vbe exemplified lin'the method and apparatusherenafterdescribed:and iof which the scope-ofapplication will'be indicatedin the re1- lowing-claimsi..

In'. the accompanying.--P drawing,` in; which is shown one'. of: the?` various 1 possible illustrative .embodiments finis-invention,

Fig; l.islrafsideffelevational View of apparatus embodying the invention;

Fig. 2 is an enlarged cross-sectional view taken on line 2--2 of Fig. 1;

Fig. 3 is a partial cross-sectional View taken on line 3 3 of Fig. 2;

Fig. 4 is a cross-sectional view taken on line d l of Fig. 3;

Fig. 5 is a View similar to Fig. 3 but `showing the top cover opened; p

Fig. 6 is an elevational cross-sectional view of one of the bus bars;

Fig. 7 is a partial cross-sectional View taken on line iL-'l of Fig. 1;

Fig. 8 is an enlarged partial view of a portion ci the apparatus shown in Fig. 7 and Fig. 9 is a sectional view of a mold used in apparatus embodying the invention.

Referring now in detail to the drawing, l! designates apparatus embodying the invention. The same comprises generally of a preheater il, a high frequency apparatus l2,vand a post-heater it. The apparatus IB is for molding articles in a mold of the type shown in my co-pending application Serial No. 610,262 led on even date herewith. A mold of this type is shown in Fig. 9 indicated by numeral le. The mold comprises generally of a body l5 made of heat resisting, insulating material such as ceramics and is formed with a mold cavity i6. It is furthermore provided with a bottom plate il made of metal and a combination metal top plate and ram i3 for the top of the mold cavity. The bottom and'top plates serve as terminals to engage bus bars in high frequency apparatus I2 as will appear hereinafter.

In accordance with the process comprising the present invention, the material or article to be molded is placed in the mold cavity ii where 'it is maintained under vertical as well as horizontal or side pressure. Anysuitable article may be molded with the improved apparatus described herein. For example, there may be molded by means of this apparatus a sole such as shown and described in my Patent No. 2,361,938 issued November '7, 1944. Such a sole comprises a braid strip of brous material Wound together with uncured rubber or thermoplastic material into the general shape of a sole. The purpose of molding is to cure the rubber or fuse the thermoplastic material under heat and pressure so as to cause the plastic material to penetrate the fibers of the braid and integrate the windings into a sole. To cure the rubber or to plasticize the thermoplastic material, such material must be brought to a predetermined curing or fusing temperature. In accordance with the present invention, the mold is preheated in the preheater Il. It then passes through a high frequency apparatus l2 and then passes through the post-heater i3. This process permits economical belt line heating method which is continuous with the curing as will appear hereinafter. The preheater is for the purpose of having the top lid and ram and the bottom plate of the mold at a temperature equal to or slightly above the temperature to which the sole or other article'to be molded will be heated in the high frequency apparatus l2. The high frequency apparatus will cause all oi the sole or like article to reach curing ternperature at exactly the same time. Should the two metal surfacesof the top lid and ram and the bottom plate not be at said temperature, these surfaces will exact or withdraw heat from the surfaces of the sole or like article contiguous thereto and reduce the temperatureof said sur-- faces below the proper curing temperatures or at least below the temperature in the interior of the sole, thereby retarding or perhaps arresting the curing at the surfaces. The purposes of the high frequency is to heat the sole to curing temperature which permits the start of the curing more quickly since the high frequency brings the temperature of the sole to curing temperature quickly. The high frequency current is on for the time necessary to bring the sole or like article to curing temperature. The post-heater keeps the two metal electrodes of the plate or mold at curing temperature or slightly higher, thereby keeping the sole at curing temperature without loss oi heat. rihe mold is kept in the post-heater for a length of time to cure the rubber or thoroughly plasticize the thermoplastic material. It will thus be seen that the purpose of the preheater is to heat the molds and not the stock or articlel to be molded.

The high frequency apparatus l2 comprises an elongated base or table 2t which may be supported by a iront Wall 2l and a rear wall 2id. Mounted on the longitudinal midsection of wall 2@ are a plurality or" spaced supports 22 for a bus bar 223. Each support 22 comprises a post 24 made oi heat resisting, insulating material. Each post 2li is attached to table 2t by means of a screw extending through a vertical opening 26 in the table. At the underside of each post 24 is a socket 2 in which is embedded an internally screw threaded sleeve 2t to which the upper end of screw 25 is screwed. At the underside of table 2i? is a recess 3B, the same being located at the lower end of each vertical opening 2t. Screwed to the lower end of each screw 25 is a wing nut 3i located in said recess. At the upper end 0i each post is e. recess 33. Within each recess is a coil compression spring 34. Mounted on the springs 3d is the longitudinal bus bar 23. The bus Ibar 23 is provided at the edges thereof with folded over lips 23a to engage the upper convolutions ci springs i. The bus bar 23 has an end portion 23h which may be connected in any suitable manner to one terminal of a high frequency or radio frequency current generator.

At the ends of table 2l]- are rollers or pulleys ilu. On the pulleys 4i) are spaced similar belts fil. The belts lll are located on opposite sides of the posts 22. Attached to the belts M are spaced cleats 152. The molds Id are adapted to be conveyed by the belts lll. The cleats aid in conveying the molds. When so conveyed, the lower terminals Il oi the molds contact the bus bar 23.

Means is provided to support the upper runs of the belts 4l. To this end there is interposed between the upper and lower runs of each belt di a block of heat resistant, insulating material. rIhe blocks l5 may be fixed to table 2U at their outer sides. As illustrated in Fig. 2 of the drawing, there is interposed between each block 45 and table 20 a longitudinal bar i6 of insulating material. On the upper surfaces of each block 45 is another bar fil. The bars 46, dl as well as block 45 are formed with registering through openings which register with openings :i3 in table 20 to receive attaching bolts 50.

Hinged to rear wall 2m as on hinge 5|, is a cover 52, Each cover 52 may comprise a top wall 53, a rear wall 54 and a front wall 55. The walls E3, 54, and 55 may be made of metal. Contacting, and attached to, the inner surfaces of said walls are insulating walls 53a, 54a, and 55a, respectively. Attached to the underside of top wall 53a are a plurality of supports 56 for an upper longitudinal bus bar 51. Each post 56 is made of heat insulating electrically resisting material. It is attached to the top wall 53a by a screw 58. Each post 56 is formed on its underside with a recess 59. A the bottom of recess 59 is a socket 60. Embedded in socket 60 is an internally screw threaded sleeve 6I. Screwed thereto is a screw 62. Attached to each screw 62 is a coil spring 63. rThe bus bar 51 is connected to the lower ends of the coil springs 63. Each bus bar 51 has lips 51a at the edges thereof turned over into engagement with the lower convolutions of said springs. The bus bar 51 extends longitudinally of the apparatus and is disposed above the lower bus bar 23.

It will now be understood that as a conveyor belt moves the molds, the upper ram I8 will contact the upper bus bar. Said upper bus bar is provided with an end 51h connected to the other terminal of the high frequency generator. For this reason, the molds passing through the high frequency apparatus I2 will receive high frequency current through the cavity I6 for heating, molding, fusing or curing the articles within said cavity. The cover 52 may be made in longitudinal sections so that each section may be separately lifted.

A heat gauge 65 may be mounted on the cover to project into the chamber 66 formed between the cover and the table 20 so that the operator may ascertain the temperature within said chamber.

The preheater II likewise comprises an elongated table 29 and a cover 52 hinged thereto. On the table portion of the preheater II is a block lil of heat insulating, electrically resisting material. The block 'in is supported on the table in any suitable manner. Furthermore, at the ends of the table are rollers 16 supporting a pair of spaced belts 11. The block is interposed between the upper and lower runs of the belt. Block 19 may be provided at the sides thereof with opstanding flanges 'i8 to serve as guides for the belt. Said block is furthermore formed in the upper surface thereof with a plurality of pairs of sockets 19 in each of which is a coil compression spring 89 supporting a plate 8l. Belt 11 is likewise provided with cleats 42 to aid in moving the molds. The molds on the belt 11 slide along plate 9 I. Beneath each plate 8| are longitudinal heating elements 84 of any Suitable type for heating the molds as they pass along plate 8I.

Attached to the inner surface of the cover 52 of preheater I I is a block 85 formed on its undersurface with sockets 86. At the bottom of each socket is a blind opening 81 in which is embedded an internally screw threaded sleeve 88. Screwed to the sleeve 88 is a screw 89. Attached to screw 89 is a coil spring 99. Supported by the pairs of adjacent coil springs 9U is a plate 9|. Plate 9I may be fixed to coils 90 in any suitable manner. Block 85 is formed with a surface 93 between sockets 86. Attached to the underside of surface 93 by means of a clamp 94 are a plurality of longitudinally extending heating elements 95. Heating elements 95 heat the upper side of the mold as the mold is conveyed through the pre-heater by the conveyor belts 11.

The post-heater I3 may be constructed substantially similarly to the preheater.

Any suitable means may be provided for transferring the molds from the preheater to the high frequency apparatus, and from the high frequency apparatus to the p ost heater I3. Fixed 6 between adjacent ends of the belts 11, 4I there may be provided a plate 98 over which the molds are pushed.

Furthermore, a single conveyor belt may be employed for the preheater, high frequency apparatus, and post-heater.

It will now be understood that the molds I4 first pass through the preheater where the mold is heated. The molds then pass through the high frequency apparatus where the material or article in the cavity I6 is subject to high frequency current, and then the molds pass through the postheater where the molds `are retained in heated condition.

It will thus be seen that there is provided an apparatus and process in which the several objects of this invention are achieved, and which is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiments above set forth, it is to be understood that all matter herein set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. A method of molding plastic material comprising preheating a mold containing said plastic material to a temperature at least as high as the molding temperature of said plastic material, subjecting the material Within the mold to high frequency current to uniformly and quickly heat the plastic material within the mold to its molding temperature, and subsequently post heating said mold to maintain said mold at the molding temperature of said plastic material for a time sufcient to complete the molding of said material.

2. In apparatus of the character described, in combination top and bottom bus bars connected to the terminals of high frequency current generator, a mold having a mold cavity, and conductors at the upper and lower ends of the mold cavity adapted to engage the bus bars, and vconveyor means for moving the mold along the bus bars.

3. Apparatus of the character described, comprising a preheater, high frequency current apparatus adjacent the preheater, and a post-heater adjacent the high frequency current apparatus, means for moving a mold successively through said preheater, high frequency current apparatus, and post-heater, means for heating the mold in the preheater, means for subjecting the mold cavity in said mold to high frequency current in the high frequency current apparatus, and means for heating the mold in the post-heater.

4. High frequency apparatus comprising a base, a pair of spaced belts over said base, a lower bar on said base and between said belts, a cover for said base, an upper bus Vbar supported by the cover and disposed above the lower bus bar, and means for connecting said bus bar to the terminals of a high frequency current generator.

5. High frequency apparatus comprising a base, a pair of spaced belts over said base, a lower bus bar on said base and between said belts, a cover for said base, an upper bus bar supported by the cover and disposed above the lower bus bar, means for `connecting said bus bars to the terminals of a high frequency current generator, and a mold on said belt, said mold comprising a mold cavity,

'aanwas :.an'd .conductors at-.the upper. and-l'owergends1of 2!"themold:'cavityhscontacting said'bus-bars.

6. High frequency apparatus comprising-top "f gand:loott'om Isupports, Aan' "elongatedv Vbus'ffbar re- Jsiliently"supportedonrsaidv bottom support, a

second bus bar resilientlywsuppcrted :onfs'aidntop us bars, and means ttor connect: said busnhars. to

port, a, pair of belts on opposite sides yoffs'a-idf-.bus

-.bars,i;^means to connect said'. busl'barsto a :high frequency :current generator and mcldnon said belts'-T said .moldz having `an4 electric a insulating l ."bi`3dy,v a mold cavity' in the body and conductors at the upper and lower ends of said cavity-and lcontacting said bus bars.

" w8.' lfI-Iigh i'frequency apparatus comprising vtop brand :bottom supports', an elongatedbus f bari resili- .-'entlysupported on saidbottom supportgafs'econd .1t-bus barresili'ently .supported .on said-topi support, :.awpar of beltsfonoppositesidespf saidfbus'bars,

'.'quency-'Jcurrent generator, arnold onl saidebelts,

sai :l'".nf1old:fhavingA `an electricl insulating Abody, a

- mold'fcavity in the body kand conductors at the =.`.;upper and'lower ends of said cavityand'co'ntactf :ing'sadibus bars, andpleats cn-saidfbelt' adapted zto engage saidniold.

' *9; lHigh :frequency apparatusI Acomprising 'an .baseg'said'cover having a top wall of heat resisting, electric insulating material, downwardlyprc- -je`cting posts attached to said top'.l wal-lr,- springs fon said last posts,rand a bus barattached to-.the A elast :mentioned springs and located -aboveth'e first bus bar.

10; High frequency apparatus comprising.' an t Velongatedbase of `heat resisting-.electrical insulating material, a plurality oispaced posts of insulating material on said base, a spring on each ..post, abus bar .su-pp orted'on said springs, belts .onopposite sides of. said bus bar,- a cover on said base, Isaid cover having atop wall ofheat resisting, electric insulating material, downwardlypro- `je'cting posts'attached to said. top wall,y sprngson said lastposts, a busbarattached to the lastmentioned springs and located abovethe firstbus bar, .-.said cover-being hinged to said base.

" 1l.v High frequencyy apparatus comprising ,an

. elongated-base of. heat `resistingwelectrical-finsulating material, aplurality ofspaced .posts of .insulatingmaterial on said base, a springen each post, a bus bar supported on said springsbelts on `opposite sides 0fl said bus bar, a cover .on..said

base, said cover having a top wall oi heat resisting, .electric insulating material,I downwardly projecting posts attached -to said top wall, springs on said y'last posts, a bus bar attached to the last 'mentioned springs andlocated above the first bus bar, amold on' said'belt,said `mold having Aamold cavity and conductors at' the Iupper and lowerends 'of saidcavity, contacting said `bus bars,

12J-High frequency apparatus `comprising an f `i elongated basefof heatresisting, electrical insulating KLmaterial, avplu'rality of spaced posts of 'lnsla'tin'g material on -said base, aspringuon each f 'Ppostrarbusbarlsupported on said springs; belts on.I

il 8 opposite sides of said-bus bar, aicover on saidhase, v said: cover having Y. a." topf: wall f. of 1. heat resisting, electric insulatingf-.material,. downwardly .proj ectfing-.postsattached to saidftop wallspringsion said 5 last fposts, abus bar. attachedtowthedast ...men-

-tioned Isprings..-and located..l above. the 1. rst bus -'.ebarfafmold on lsaid belt,y said moldhaving-a mold cavity andfconductors .at the upperv and lower-.ends fvotsaid'cavity, -contactingisaid busbarsyand cleats l lgfvfon said-.belts adapted to engagesaid mold.

1 13..-fHigh. frequency.:y apparatus l.comprising .an -elongated base of fheat-resisting.,`r electrical: in- =sulating..material,. a .plurality ofispaced .-posts. of

- :insulating material yon saidbase; a vspringoneach post, abusbarJ supported on. saidpsprings, lbeltson opposite Ysides of said bus bar. a cover on saidbase, f said coverhaving a top Wall of heat.resisting,-.elec H tric.v insulating 1.materia-l, downwardly.. .projecting posts lattached to. said top wall, springs onsaidlast posts,.a.bus`A bar .attachedto the-=last :mentioned 2- ffsprings .and .locatedfabove .the .first bus-.bam said cover being hinged .to said.. base, rand.. insulating 4blocks. between .theV yupperandlower runs of. said .belts. 14 .I-n'apparatusof the character-described, a

preheaten high frequencycurrent. apparatus and apostheatennall arranged in..=tandem,..amold having a mold cavity, means toconvey-.said -mold successively.. through `4said .preheaterf 1apparatus and. .post-heater, and means to.. subjectmaterial V`-Withinsaid cavity to high frequencycurrent as said mold isv conveyed through said apparatus.

15. In apparatus of the character described, a preheater, highA` frequency currentapparatus and 35. a post-.heater,-all. arranged vini, tandem, '.a -smold f .having: a mold cavity, means lio-.conveyl said-mold Vlsuccessively vthrough` said -preheater,.apparatus andwpostheater, means `to subjectmaterial -within said cavitytohigh frequency.currentras'said mold 0. is` conveyed .through said.,fapparatusf.I said "last .means including .bus .bars fin said apparatus iconl nected to. theterininals ofa highI frequencycurlrent. generator,v and 'conductorswon .'saidlmold, -wabove and below .said cavity; in yconta-ct with said bllS fbrllS.

.16. .A'=:method of'cmolding -a .curable :material comprising continuously movingv a moldf'containing' the curable ymaterial `through yarpreheating zone which will 'heatthemold:to=substantiallywthe s curing temperature offsaidA curable material, con- .tinuing .the movement. of -rsaid .I heatedf-mold through a zone wherein the material isi-.subjected to high vfrequency*curr-ent which will-heat'the'material tol a temperature which willinitiatewthe cure oli-said material and' subsequently-continuing the f 4movement of fsaid- :moldy through :ai ipost. heating f. .zone .wherein thei material is zmaintained at-v its curing temperature.until-saidmaterial is cured.

U.17.. A method .of molding va icurablev material 0. comprising'thefstepsvoffpreheating a mold con- ..tainingf-.the curable material :tof-substantially a .temperaturefequivalent to thecuring :temperature rvvofsaidmaterial'; thenisubjecting .thermateri'al to auhighffrequency current :which .wi1l'-quickly;.and .-^-.uniformly wheat f saidr vmaterialtom temperature sufficient to;A initiate thenure thereofa'andc'subse- Y I-quently .hea-ting said mold. to la :temperature .and #for aperiod'oftime whichlwillicompletethe'cure of the material. e 18; .Ar method Vofumolding fair-.curable :material comprising.- thesteps of preheating al-lcavity. mold containing the .material iunti-lthe inner :surfaces "of saidmold have'attained-a temperaturenot less i than thecuringn temperature of.1 said curable .ma- -teria1,1thenl subjecting said 'mold-to a highffrequency current which will uniformly heat said material to a temperature sumcient to initiate the `cure of said material and thereafter heating said mold to at least the curing temperature of said material, and for a period of time which will complete the cure of said material.

19, A method of molding a curable material comprising the steps of moving a mold containing the material between and in contact with opposed heated plates to heat said mold to the curing temperature of said material, then moving said mold between and in contact with opposed high `frequency electrodes to quickly and uniformly heat said material to initiate the cure thereof and thereafter moving said mold between and in contact with opposed heated plates to complete the cure of said material.

20. A method of molding a curable material comprising the vsteps of moving a mold containing the material through a heated Zone to heat the mold to the curing temperature of said material, thereafter moving Said mold through a high frequency zone to uniformly and quickly heat the material in the mold to said temperature to initiate the cure thereof and subsequently moving said mold through a heated zone to complete the cure of said material.

JON GREGG.

REFERENCES CITED The following references are of record in the lfile of this patent:

UNITED STATES PATENTS Number Name Date 1,760,234 Frederick May 27, 1930 2,228,614 Soubier et al Jan. 14, 1941 2,292,366 De Wyk, Jr Aug. 11, 1942 2,342,920 Clark Feb. 29, 1944 FOREIGN PATENTS Number Country Date 276,440 Great Britian Aug. 29, 1927 517,798 Great Britain Feb. 8, 1940 OTHER REFERENCES British Plastics Heatronic Moulding, June 1943, Electric Heat Digest.

Modern Plastics, Progress in Heatronic Molding, El. Heat Dig. (pages 108 to 113 and 160). 

